Partovi, 32, said he's not leaving because of any turmoil at MSN. He said he's leaving to start his own company, probably an Internet venture.

"It's really more 'I want to do my own thing,' " Partovi said.

The resignation was announced at a staff meeting last week. Partovi is remaining at the company for several more weeks to finish projects he's excited about, including a revamped version of the MSN.com home page and updates to the Start.com portal developed by his group.

Partovi's leaving fits a pattern at MSN, where the departure of senior content managers has followed moves to refocus the business.

MSNBC.com Editor Merrill Brown resigned in 2002 after his staff was reduced and MSNBC.com was folded into MSN.

Slate founding editor Michael Kinsley also left in 2002, two years before Microsoft sold its online magazine to The Washington Post Co.

More recently, MSN content manager Scott Moore resigned in April to join Yahoo!

Partovi was well known in the late 1990s as a key player in the "browser wars" with Netscape Communications, but he's kept a relatively low profile at MSN.

The Harvard-educated computer scientist was group program manager for the Internet Explorer browser when Microsoft was fighting its U.S. antitrust case.

In 1999, he left to start Tellme Networks, a San Francisco telecommunications venture.

Tellme drew attention, partly because his partners included former competitors from Netscape. Partovi returned to Microsoft in 2002.